1. Field of the Invention
The present invention relates to novel catalysts for the treatment of gases, in particular gaseous industrial effluents containing sulfur compounds, to catalytically convert such sulfur compounds into compounds that are more easily removed from said effluents.
This invention especially relates to novel catalysts for the direct oxidation of hydrogen sulfide or carbon compounds of sulfur into elemental sulfur, SO.sub.2 and/or SO.sub.3.
2. Description of the Prior Art
Certain industrial effluents and in particular the effluents emanating from Claus catalysis reactions, known as "tail gas", contain sulfur and/or oxidizable polluting sulfur compounds, which must be converted by oxidation into easily removable compounds, such as sulfur dioxide and/or sulfur trioxide.
The sulfur compounds typically present in such effluents are principally hydrogen sulfide and organic sulfur compounds, such as carbon disulfide, carbon oxysulfide and/or mercaptans.
These effluents may also be treated to convert the sulfur compounds into elemental sulfur by direct oxidation, as elemental sulfur is readily eliminable or recoverable, for example by condensation.
Several processes for the oxidation of these types of compounds are already known to this art. The simplest such process entails incinerating the effluents at elevated temperatures.
However, if the hydrogen sulfide content is too low, it is difficult to maintain a flame temperature high enough to provide a stable combustion of the sulfur compounds.
To treat gases having low hydrogen sulfide concentrations, catalytic processes for the oxidation of sulfur compounds into S, SO.sub.2 or SO.sub.3 have been proposed to the art.
Among the catalysts proposed, those based on titanium oxide would appear to be particularly effective. Compare EP 115,449, 60,742, 78,690, each of which describe different catalysts based on titanium oxide for use in the oxidation of hydrogen sulfide.
Other catalysts have also been proposed to the art. Thus, U.S. Pat. No. 4,092,404 describes an oxidation catalyst based on vanadium, and EP 39,266 a catalyst based on iron. These catalysts are generally used in the form of a bed of particles placed in a column, with the gaseous flowstreams to be treated being transported through said column.
These catalyst beds known to the prior art included catalyst particles in the form of cylindrical or spherical granules formed by molding or extrusion. However, the amount of the catalyst that it is possible to introduce into a column or a converter is limited by the pressure differential created thereby in the packing of the column, which gives rise to an oxidation yield of the sulfur compounds less than the theoretical yield calculated by the laws of thermodynamics.